Emission of greenhouse gases (GHGs) from inland waters is recognized as highly important and an understudied part of the terrestrial carbon (C) biogeochemical cycle. These emissions are still poorly quantified in subarctic regions that contain vast amounts of surface C in permafrost peatlands. This is especially true in NE European peatlands, located within sporadic to discontinuous permafrost zones which are highly vulnerable to thaw. Initial measurements of C emissions from lentic waters of the Bolshezemelskaya Tundra (BZT; 200,000 km 2) demonstrated sizable CO 2 and CH 4 concentrations and fluxes to the atmosphere in 98 depressions, thaw ponds, and thermokarst lakes ranging from 0.5 × 10 6 to 5 × 10 6 m 2 in size. CO 2 fluxes decreased by an order of magnitude as waterbody size increased by > 3 orders of magnitude while CH 4 fluxes showed large variability unrelated to lake size. By using a combination of Landsat-8 and GeoEye-1 images, we determined lakes cover 4% of BZT and thus calculated overall C emissions from lentic waters to be 3.8 AE 0.65 Tg C yr −1 (99% C-CO 2 , 1% C-CH 4), which is two times higher than the lateral riverine export. Large lakes dominated GHG emissions whereas small thaw ponds had a minor contribution to overall water surface area and GHG emissions. These data suggest that, if permafrost thaw in NE Europe results in disappearance of large thermokarst lakes and formation of new small thaw ponds and depressions, GHG emissions from lentic waters in this region may decrease.

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The problems of modeling the spatial structure of the fields of thermokarst lakes in the permafrost zone of Western Siberia based on the geo-simulation approach are considered. The basic principles for the development of a geo-simulation model for the structure of thermokarst lakes fields are outlined. Experimental data on the properties of lake fields obtained on the basis of the integration of high- and medium-resolution satellite images are presented. Data analysis showed that the empirical histogram of the distribution of lakes by size is approximated by the lognormal distribution law by the Pearson criterion with a probability of 0.99. This law of distribution, in contrast to the power law of size distribution of lakes that is commonly used in such studies, also takes into account small lakes, considered as intense sources of methane emission into the atmosphere from thermokarst lakes. An example of modeling the field of thermokarst lakes with a lognormal law of their size-distribution is given.

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